An approach to the assessment of high-level radioactive waste containment.I: Waste package degradation

A description is presented of the various models (i.e. thermal, chemical en vironment, humid-air and aqueous corrosion) used in the engineered barrier system performance assessment code (EBSPAC) to represent processes that gov ern the failure of waste packages (WPs) and, ultimately, the release of rad ionuclides from the engineered barrier system (EBS). These models are speci fically adapted to the US Department of Energy (DOE) WP design, adopted in 1996, for the proposed repository at Yucca Mountain (YM), NV. The design co nsists of a double-wall overpack composed of two concentric containers of d ifferent metallic materials in a horizontal drift emplacement. EBSPAC was d eveloped to deterministically evaluate the performance of the engineered ba rriers and to be used as the source term module incorporated in the Center for Nuclear Waste Regulatory Analyses (CNWRA)/Nuclear Regulatory Commission (NRC) total performance assessment (TPA) code. EBSPAC essentially consists of two separate codes. The code dealing with WP failure calculations is th e focus of this paper and the other, dealing with radionuclide release, is described in a companion paper. An example problem is presented to illustra te the results obtained with the code analyzing the influence of several cr itical input parameters, related to the repository and EBS designs and the resulting environmental conditions, on WP failure. (C) 2000 Elsevier Scienc e S.A. All rights reserved.